/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    StructureProducer.java
 *    Copyright (C) 2011 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.gui.beans;

import weka.core.Instances;

/**
 * Interface for something that can describe the structure of what is
 * encapsulated in a named event type as an empty set of Instances (i.e.
 * attribute information only). For example, batchAssociationRulesEvent can be
 * described as LHS (String), RHS (String) and a number of metrics (Numeric);
 * dataSetEvent, instanceEvent, trainingSetEvent etc. are all straightforward,
 * since they already encapsulate instances; textEvent can be described in terms
 * of the title (String) and the body (String) of the text. Sometimes it is not
 * possible to know the structure of the encapsulated output in advance (e.g.
 * certain filters may not know how many attributes will be produced until the
 * input data arrives), in this case any implementing class can return null to
 * indicate this.
 * 
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}com)
 * @version $Revision: 7439 $
 * 
 */
public interface StructureProducer {

	/**
	 * Get the structure of the output encapsulated in the named event. If the
	 * structure can't be determined in advance of seeing input, or this
	 * StructureProducer does not generate the named event, null should be
	 * returned.
	 * 
	 * @param eventName
	 *            the name of the output event that encapsulates the requested
	 *            output.
	 * 
	 * @return the structure of the output encapsulated in the named event or
	 *         null if it can't be determined in advance of seeing input or the
	 *         named event is not generated by this StructureProduce.
	 */
	public Instances getStructure(String eventName);
}
